The scope of this document is to define performance requirements of Large Power Transformers in compliance with prEN 50708-1-1:2019. NOTE This document covers the transformers under the EU Regulation N. 548/2014 and Amendment of 2019, gives additional specific guidance for single phase transformers, autotransformers, multi winding transformers and for transformers with OD and OF cooling systems, necessary for the correct application of energy efficiency requirements to these categories of transformers.